The main objective of this research proposal is to characterize B and T human lymphocytes by means of their membrane properties. In addition, the markers present on lymphocytes from patients with leukemias, lymphomas or with primary and secondary immunodeficiency disorders will be studied to determine the origin of lymphocytes and conceivably obtain relevant information about the pathogenesis of these diseases. It is hoped that the information obtained will permit a revaluation and new classification of cell disorders of the lymphoid system, with probable implications for their diagnosis, prognosis and treatment. The research procedures involve only human materials obtained in the course of diagnosis or treatment (samples of peripheral blood and surgical specimens).